The invention relates to a valve arrangement of a hydraulic system, constructed as a step valve, including a housing which is provided with two pressure connections and has at least one valve seat to which a closing element is allocated which, in a closed position, has a first valve surface which is smaller than a second valve surface, which it has in a position where the closing element is displaced from the valve seat.
The use of one way valve, also called a non-return value or relief valve, is known in hydraulic systems to make a pressure medium flow possible and to block a return flow. Known valves of this type have a spring actuated closing element which lies sealingly against the sealing seat of the one way valve in its closed position. The construction of the valve requires that the opening pressure substantially depends upon the initial stressing force of the spring and the valve surface acted upon by pressure fluid. In this way, an increasing pressure flow resistance appears with the rise in the flow volume. This property is disadvantageous for a number of applications.
From DE-A 27 28 486 a type of valve arrangement is known in which a closing element lies sealing on a housing-side valve seat in the closed position. The pressurized fluid flows toward the closing element via an entrance in the housing and acts upon a valve surface which is smaller than a second valve surface which appears after the pressurized fluid displaces the closing element from the valve seat. The second valve surface at the same time corresponds to the diameter of the spherical closing element, whereby immediately after lifting the closing element from the valve seat, the flow-through cross section is not yet set up, because the closing element must be guided through a stepped section of a step boring having a diameter which is only slightly larger than the diameter of the closing element. After a further displacement of the closing element in a next larger section of the step boring, a new flow-through cross section is set up. The familiar one way valve makes possible an uncontrolled shifting of the closing element in the open position, whereby this can knock against the housing, which leads to a disadvantageous development of noise.